The Biotechnology Unit is responsible for: (a) Large-scale production of procaryotes (bacteria), and eucaryotes (mammalian cells, insect cells); (b) Large-scale recovery and purification of biologically active compounds (proteins, polysaccharides, etc.) from various sources; (c) Process development work associated with (1) bacterial growth, (2) eucaryotic cell growth, and (3) extraction and purification of biologically active compounds, especially proteins. The process development work is conducted to develop a procedure suitable for large-scale preparation and production of material suitable for clinical trials; and (d) Research and development work not necessarily linked to a current process development project, but work that has long-term implications for fermentation processes and protein purification. During the last year the Unit performed 212 different large-scale preparations, including microorganisms (especially E. coli-carrying recombinant DNA) grown in volumes ranging from 5 to 300 liters, eucaryotic cells grown in volume up to 50 liters and processing of various biological materials. Special effort was devoted to the development of a suitable process for the extraction and purification of large amounts of two proteins needed for clinical trials. The first is S antigen from the human retina and the second is a modified toxic version of Pseudomonas aeruginosa exotoxin A.